Polarization diversity between orthogonal polarizations is a key requirement to various antenna applications. For achieving polarization diversity, antennas are often placed orthogonal to each other, which in many balanced antenna designs, rotates the fields by 90 degrees providing true polarization diversity. Some designs take it one step further and overlap antennas (in the min Electric field region) to occupy minimum space and/or volume. One such example is shown in FIG. 1, i.e. an orthogonal dipole arrangement 10. The arrangement 10 includes orthogonal half-wavelength dipole antennas 12, 14 with no corresponding Radio Frequency (RF) choke problems. This is due to the half-wavelength dipole antennas 12, 14 each including balanced feeds 16, 18 at a center portion, i.e. the half-wavelength dipole antennas 12, 14 do not interact electrically. However, this is not possible for a conventional slot antenna 20 as depicted in a top view in FIG. 2 and a side view in FIG. 3. The slot antenna 20 includes a horizontal slot antenna 22 and a vertical slot antenna 24 disposed on an RF ground 26. Each of the antennas 22, 24 are fed at a side point with feeds 28, resulting in the horizontal slot antenna 22 acting as an RF choke to the other half of the vertical slot antenna 24 and vice versa. That is, the antenna 20 forms a λ/4 wavelength cavity ending in an RF short.
Accordingly, there is a need for a cavity backed cross-slot antenna apparatus and method overcoming the aforementioned limitations.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.